I just thought I'd point out, re: VFT root rot in LFS, that the long-fibered sphagnum is what is probably rotting on you. LFS breaks down very quickly when constantly submerged, particularly when submerged and compacted, and leads to algal growth among other things. VFTs are fine in moist soils, and fine in LFS, but LFS rapidly decaying into pond sludge is another matter.
Best luck,